1. Technical Field
The present disclosure relates to a sorting device that sorts small pieces made of a specific material type from sorting objects constituted by collecting a plurality of small pieces, and particularly, relates to a sorting device that sorts small pieces of a specific resin type from sorting objects obtained by crushing used home electric appliances or the like.
2. Description of the Related Art
Recent economic activities based on mass-production, mass-consumption, and mass-disposal have caused global environmental problems such as global warming, resource depletion and the like. Under such a situation, home electric appliance recycling has attracted attention, and recycling of a used air conditioner, television, refrigerator, freezer, and washing machine is required for construction of a recycling-based society.
Conventionally, a useless home electric appliance is crushed into small pieces in a home electric recycling factory, and then the small pieces are separated by material type, using magnetism, wind power, vibration or the like for resource recovery. Particularly, use of a specific gravity sorting device or a magnetic sorting device allows small pieces made of metal to be separated with high purity by material type such as iron, copper, aluminum and the like, which realizes a high resource recovery rate.
On the other hand, in a resin material, small pieces made of polypropylene (hereinafter, referred to as PP), which is a light specific gravity matter, are sorted from a high specific gravity matter in specific gravity sorting using water to be collected with relatively high purity. However, in the specific gravity sorting using water, there are major problems that a large amount of discharged water is produced, and that small pieces made of polystyrene (hereinafter, referred to as PS) and small pieces having a close specific gravity such as small pieces made of acrylonitrile-butadiene-styrene (hereinafter, referred to as ABS) cannot be separated.
A sorting method in view of the above-described problems regarding the resource recovery of the resin materials has been proposed in Patent Literature 1. In a technique described in Patent Literature 1 (WO2014/174736), a material type is detected by an identification device, which enables two types of small pieces made of resin materials that cannot be sorted in the specific gravity sorting to be simultaneously sorted.
FIG. 6 is a schematic configuration diagram of a conventional sorting device according to Patent Literature 1.
This sorting device sorts a specific material type matter and another material type matter from sorting objects in which the specific material type matter and the other material type matter other than the specific material type matter are mixed.
Conveyor 101 conveys small resin pieces 102 as the sorting objects placed on conveyor 101 in one direction. Composition of small resin pieces 102 is identified, and at the same time, position information on conveyor 101 is acquired when small resin pieces 102 pass under identification device 103.
Small resin pieces 102 that have reached conveyor forefront portion 104 in a conveyance direction of conveyor 101 fly out horizontally at the same velocity as conveyance velocity V100 of conveyor 101.
Above conveyor forefront portion 104, first assist nozzle 106 that generates airflow 109 at wind velocity V101 that matches conveyance velocity V100 of conveyor 101 is disposed. First upper rectifying plates 107A are disposed along a flight path of small resin pieces 102 above the flight path, and lower rectifying plate 107B is disposed along the flight path obliquely below conveyor forefront portion 104 under the flight path of small resin pieces 102. The above-described configuration enables airflow 109 at the wind velocity that matches the conveyance velocity of conveyor 101 to flow along the flight path of small resin pieces 102 inside the flight path.
Small resin pieces 102 thrown out in the horizontal direction from conveyor 101 falls, flying. On this occasion, pulse air is injected from the nozzles by a command from identification device 103 at a moment when the resin of the relevant specific material type among small resin pieces 102 passes positions where the relevant resin receives the pulse air of the nozzles of first nozzle group 105A and second nozzle group 105B, and only the resin of the relevant specific material type is shot to be collected in a section partitioned by partition plates 108.
If first assist nozzle 106, first upper rectifying plates 107A, and lower rectifying plate 107B are absent, small resin pieces 102 receive the same wind velocity V100 as the conveyance velocity of conveyor 101 from a front in a travelling direction immediately after flying out from conveyor 101, and they receive air resistive force differently, depending on shapes, areas, or weights of small resin pieces 102. In this case, since the flight path differs in respective small resin pieces 102, flight variation is caused, which decreases shooting accuracy at the positions where small resin pieces 102 receive the pulse air of first nozzle group 105A and second nozzle group 105B described later.
However, when first assist nozzle 106, first upper rectifying plates 107A, and lower rectifying plate 107B are installed, first assist nozzle 106 supplies airflow 109 at window velocity V101 matching the conveyance velocity of conveyor 101 in the flying-out direction of small resin pieces 102, and thus, a relative velocity between small resin pieces 102 and airflow 109 at the time of flying-out is almost 0, and the air resistance is also almost 0. Moreover, since first upper rectifying plates 107A and lower rectifying plate 107B maintain airflow 109 at window velocity V101 matching conveyance velocity V100 of conveyor 101 along the flight path, the flight in a state where the air resistance is almost 0 is realized across the flight path.
This action can prevent small resin pieces 102 from receiving the air resistive force inside the flight path regardless of the shapes, the areas, or weights of the resin, thereby suppressing the flight variation of the resin.
As a configuration example, for example, there is an example in which only the small resin pieces 102 of PS among small resin pieces 102 are shot by first nozzle group 105A, and small resin pieces 102 of PP among small resin pieces 102 are shot by second nozzle group 105B. Based on a time when resin small pieces 102 pass under identification device 103, times when small resin pieces 102 pass the positions where small resin pieces 102 receive the pulse air of first nozzle group 105A and second nozzle group 105B are calculated or measured in advance. Subsequently, based on the position information on conveyor 101 measured in identification device 103, at the moment when relevant small resin pieces 102 of PS among small resin pieces 102 pass the position where they receive the pulse air of first nozzle group 105A, and at the moment when relevant small resin pieces 102 of PP among small resin pieces 102 pass the position where they receive the pulse air of second nozzle group 105B, the pulse air is injected to respective relevant small resin pieces 102. With the above configuration, relevant small resin pieces 102 are shot by the pulse air, and the shot resins are collected by type into the sections partitioned by partition plates 108.
The above configuration enables two types of the specific material type matters and the other material type matter to be simultaneously sorted with high accuracy from the sorting objects in which the specific material type matters and the other material type matter are mixed.
However, from consideration by the inventors, it has been clear that in the above conventional configuration, as to the suppression of the flight variation of small resin pieces 102, a flight distance from conveyor forefront portion 104 is realized only in a range of 400 mm to 500 mm at the most, and that because of the limitation of the distance, at most two pairs of nozzle groups 105A, 105B that shoot small resin pieces 102 can be installed. If three pairs of nozzle groups are installed, the flight distance with the flight variation suppressed needs to be at least 600 mm to 700 mm.
In order to realize the above-described flight distance, as shown in FIG. 7, second upper rectifying plate 107C is installed next to first upper rectifying plate 107A along flight path to extend a rectifying effect, and third nozzle group 105C is installed to consider the sorting accuracy.
Here, assuming that conveyor forefront portion 104 is an origin, on an X axis, the conveyance direction is positive, and on a Z axis, a downward direction of a vertical direction is positive, and coordinates of conveyor forefront portion 104 are P100 (X, Z)=(0 mm. 0 mm). At this time, as one example, a position where the object matter passes when receiving the pulse air from first nozzle group 105A is P101 (X, Z)=(250 mm, 60 mm), a position where the object matter passes when receiving the pulse air from second nozzle group 105B is P102 (X, Z)=(450 mm, 160 mm), and a position where the object matter passes when receiving the pulse air from third nozzle group 105C is P103 (X, Z)=(600 mm, 250 mm). Moreover, as one example, conveyance velocity V100 of conveyor 101 is V100=3 m/s, airflow 109 equivalent to the conveyance velocity of conveyor 101 is supplied from first assist nozzle 106 at wind velocity V101=3 m/s±15% to conduct an experiment equivalent to Patent Literature 1.
As used small resin pieces 102, resins different in size that are 10 mm squares to 100 mm squares are used, because the resins having small grain sizes produced when home electric appliance resins are crushed into small pieces by a crusher are objects.
The time when small resin pieces 102 fly out of conveyor forefront portion 104 is 0, the times when small resin pieces 102 pass the positions where they receive the pulse air of first nozzle group 105A, second nozzle group 105B, and third nozzle group 105C are defined as t101, t102, and t103, respectively, and in order to measure the times, a high-speed camera (HAS-L1M 500FPS by DITECT) and image analysis software are prepared for measurement.
In FIG. 8, if variation in arrival time of small resin pieces at positions P101, P102, and P103 where the pulse air from first nozzle group 105A, second nozzle group 105B, and third nozzle group 105C is received is indicated by 3σ, and with the flight velocity in the X direction V100=3 m/s, the conversion to the flight variation of small resin pieces 102 is performed.
As a result, in some of small resin pieces 102, at position P101 where the pulse air of first nozzle group 105A is received, a shooting timing shift by 6.76 ms is caused. Moreover, at position P102 where the pulse air of second nozzle group 105B is received, a shooting timing shift by 12.18 ms is caused. Moreover, at position P103 where the pulse air of third nozzle group 105C is received, a shooting timing shift by 16.25 ms is caused. Converted to the distance, at time points when the nozzle groups inject the pulse air, a shift by up to 19.9 mm is caused at position P101 where the pulse air of first nozzle group 105A is received, a shift by up to 35.8 mm is caused at position P102 where the pulse air of second nozzle group 105B is received, and a shift by up to 47.8 mm is caused at position P103 where the pulse air of third nozzle group 105C is received.
For installing three or more stages of nozzle groups and simultaneously sorting three types of small resin pieces 102, the flight distance to third nozzle group 105C is required to be at least 600 mm, and across this flight distance, the flight variation needs to be suppressed. The inventors have considered that for this, wind velocity V101 of airflow 109 inside the flight path needs to be further controlled.
FIG. 9A is a schematic diagram showing gravity and fall velocity acting when an object is thrown out in the horizontal direction from conveyor 101 if a gravitational acceleration is g and there is no air resistance. The horizontal direction is an X axis on which a right hand in the horizontal direction is positive, and the vertical direction is a Z axis on which a downward direction in the vertical direction is positive. If a velocity of the object thrown out in the horizontal direction from conveyor 101 is Vx, in the X axis direction, constantly Vx=V100. As to velocity Vz of the object in the vertical direction at a position where the object advances by X in the horizontal direction, Vz=g (X/V100). Thus, the fall velocity in a traveling direction of the object, that is, velocity in a fall parabola tangent direction V is represented by expression (1).V=[{g(X/V100)}2+V1002]1/2  (1)
FIG. 9B is a graph showing calculation of the fall velocity, where, as one example, conveyor velocity V100=3 m/s, as to an initial velocity of small resin pieces 102 as well, V100=3 m/s, the air resistance is ignored, and the fall velocity follows expression (1).
At position X=250 mm where the pulse air of first nozzle group 105A is received, fall velocity V=3.11 m/s. At position X=450 mm where the pulse air of second nozzle group 105B is received, fall velocity V=3.34 m/s. At position X=600 mm where the pulse air of third nozzle group 105C is received, fall velocity V=3.58 m/s. In the method of Patent Literature 1, since the wind velocity of airflow 109 matches 3 m/s along the flight path, the longer the flight path becomes, the larger shift is caused between wind velocity V101 of airflow 109 and fall velocity V, and the air resistance is received, which is assumed to be a cause of the flight variation.
Namely, in the conventional configuration, when small resin pieces 102 as the sorting objects fall along the flight path, even if the wind velocity of airflow 109 supplied from first assist nozzle 106 is set to be equal to the initial velocity of the resin, as the flight distance becomes longer, fall velocity V is increased by the gravity, and the fall velocity becomes higher than the wind velocity of the airflow. Therefore, the longer the flight path becomes, the air resistive force is acted differently, depending on the shape, the area, or the weight of the resin. This poses a problem that the flight variation is caused, so that the shooting accuracy is decreased at a flight distance described in Patent Literature 1 or longer.